Hi all,


I have a futaba GY 404 avcs gyro with a S9254 servos. When I move the rudder stick everything works fine except that the servos is not going back to neutral. Is that normal?? Sorry for my ignorance but I am new to heli.

Thanks

Serge

Ok ... I'm going to assume it's really a 401.

This is a normal servo response IF you are in AVCS (Heading Hold) mode AND the heli is not allowed to YAW (on the ground or your workbench).
It is NOT normal if the gyro is in RATE/Normal mode or if the heli is allowed to YAW (in flight).

AVCS mode: When you move the rudder stick in AVCS / HH mode ... the servo command (rudder channel) is interpretted by the gyro as a "magnitude of rate" (ie how fast you want to YAW). So the gyro will give a command to the servo (as required) to cause the heli to YAW at that particular YAW rate (defined by stick position). So if the heli is on the ground or on your work bench and you move the rudder stick ... the gyro will move the servo while monitoring YAW rate. Upon "sensing" 0 YAW rate (it's on the ground or workbench) ... the gyro adds more servo movement in order to get the heli to YAW. Still sensing 0 YAW rate, the gyro ends up deflecting the servo to the limits ... and there it stays.

If you are on the workbench and testing in HH mode and your servo seems to go to one side and stay there ... center you rudder stick and manually YAW (nose left/right) your heli with your hands and see if the gyro responds by changing the servo in it's "attempt" at maintaning 0 YAW rate (stick is centered = 0 YAW rate command).

In Rate Mode: The servo should pretty much follow the stick where ever it goes with little gyro interaction. The mechanical alignment/trimming of the heli should be made in RATE mode and then HH mode select for flying.

Sorry its a 401 in AVCS mode. Thank you very much for the detailed explanation. I understand now.

Serge